The rheological properties of oils, particularly lubricating oils vary with temperature. Since many oils are used over a wide range of temperatures, it is important to preserve the rheological properties of the oils over such a wide range of temperatures. For mineral oil lubricants, additives are typically added to preserve the rheological properties of the oils.
One indication of the rheological properties of a lubricating oil is its temperature/viscosity relationship, referred to herein as “viscosity index,” which can be determined using standard techniques. The higher the viscosity index of the oil, the less the viscosity of the oil depends on the temperature. For oils having a low viscosity index, a viscosity index improver composition is included in the oil. However, not all viscosity index improvers perform the same. As uses for lubricating oils continue to expand and become more complex, there continues to be a need for improved lubricant compositions.